Worked with a kid like that. Our experience is he had a lot of difficulty with movement control while he was growing very fast. He struggled with barbel work and good form.

Each kid is different. So you will have to closely watch. As has been said I would work on basic drills and movements for coordination. If you do that when the kid finishes his big growth spurt at 14-15 he will be ready to add strength fast.

If you try to add strength too early it will be a bad experience. Remember he is not like an adult. When his body is ready he will be able to add strength and mass at an amazing rate. What would take you or I years he will do in months when the time is right.

Keep him healthy, teach him good technique and make sure he has fun.

Handling a kid like this correctly is a true demonstration of coaching skills and wisdom.